Process of making friction facings



- Llfdg d o more snares PATENT @FlflGE.

G. SWIFT, @F @AIZL'BFREJDQE, llIAhSlSAGEUSETTS, ASSTGNQR TQ Wit-WENFABRIC @(Q'EEZPANY, @lr" WAELEWLE, LEASSAGIEZUSETTS, A RPEATEN orvatnssaonusarrs.

ilo Drawing.

various types of clutches and brakes, it is the usual practise to lineor face a brake or clutch element with a material capable of resistingwear, giving the desired co-efficient of friction, and adapted to resistthe relav tively high temperatures which are created between theelements of the clutch or brake under certain conditions of service.Particularly important examples of this practise are found inthecclutches and brakesused in motor vehicles.

At the present time the more usual clutch facings and brake linings aremade from a heavy asbestos fabric, the yarn from which the fabric iswoven usually being reinforced by a fine wire and the fabric beingdoped, that is, impregnated with a binder, which usually is cured byheat and which serves to bind together the fibres of asbestos or othermaterial used in the fabric and to consolidate the material and enableit better to resist wear. The co-eficient of friction of the facing alsodepends largely upon the nature of this dope, or impregnatin compound,and the curing treatment whic it undergoes.

lit is obvious that the s nnning and weaving operations'necessitate theuse of a relatively long fibre asbestos; and while it was proposed anumber of years ago to make friction facings of this character fromshort fibre asbestos by processes that would elimi nate the necessityfor the spinning and weav-' ing operations, such facings have never beenused to any substantial extent until very recently, when theextraordinary rise occurred in the price of crude-or long fibreasbestos. Of the various processes heretofore suggested for 'maln'ngthese faclngs from short asbestos fibre, the most successful process nowin use, of which I am aware, consists essentially in forming an asbestosboard or sheet, usually in a paper mag hine, and then impregnating thesheet w so Application filed November 28 Specification of LettersPatent. Patented Aug, $2, 192%,

(5, ram. serial No. 264,245.

formed with a binding material, dieing out rings or other facing partsof the desired shape and dimensions, from this sheet stock, and bahngand pressing the parts so died out to cure the binder and consolidatethe facing. in some instances the facings are died out before theimpregnating operation is performed.

While friction facings manufactured in the manner just described havemet with some degree of success, it has been impracticable to producecommercially a facing of uniform or homogenous character, due chiefly tothe difiiculty of uniformly impregnating the facing with the bindingmaterial, It is obvious that since the binder performs a very importantfunction in facings of this character, the failure to realize a uniformimpregnation of the material will result in varyin the wearing qualitiesand co-eficient riction of, the facing at diflerent facings of a moreuniform and homogeneous character than those heretofore proposed,

and in: which a uniform impregnation of the facing will be efiected.

The nature of the invention will be readily understood from thefollowing description and the novel features of the invention will bepointed out more particularly in the appended claims.

According to the present invention the materials that form the body ofthe facing, and which will vary in character and proportions accordingto the formulas of different manufacturers, are all placed in a heateror an agitator and mixed with a relatively large quantity of liquid.Whether or not a heater is used will depend upon the nature of thematerials and the condition in which it is desired to brin themtogether. llf the materials. are relative y coarse 1t may be necessaryto run them throkgh a heater before they are brought into e agitator.

the other materials that of for the binder, this solvent being used inthe present recess in place of the water that is ordinari y used in thepaper making process. A crude form of asphaltum is very commonl -used asa binder and is dissolved in napht a, gasoline, or benzol preparatory toperforming the im regnating operation. Consequently, when t 's binder isused, a solvent for it is em loyed as the liquid in which the finelydivided materials are held in suspension durin the formation of thesheet stock. This mlxture ofliquid solvent and the materials held insuspension thereby are run through a paper makin machine, preferably ofthe cylinder type in which a sheet of the required thickness is builtup.

As is well understood by those skilled in this art the machine strainsout enough of the solid matter to form a very thin flimsy sheet and thissheet is transferred to a cylinder on which it is wound to build up aboard or sheet of the required thickness The liquid, afterpassingthrough the screen and depositing the solid material carriedthereby, or at any rate a verylarge percentage of it, is collected insuitable receptacles and returned to the agitator where it is againmixed with raw materials in readiness to repeat the process.

It is obvious that this process produces a sheet stock in which anabsolutely uniform impregnation of the stock with the binder isefi'ected. That is, the binder being present in the form of a solutionor held in suspension in the liquid which also holds the other materialsin suspension, ensures a very intimate contact of the binder with thefibers and particles of materials that make u the sheet. Consequently,when a sheet 0 the required thickness has been built up on the cyllnderof the paper machine and is removed from this cylinder in the usual way,the binder is distributed uniformly through the entire depth of thesheet.

Preferably facings of the desired form are died outof this sheet stockwhile it is still damp and before the cement, in case such material isused, has had an opportunity f to set. These facings are then pressedand baked. In the case of clutch rings, for which the present recess isparticularly adapted, the rings a r being died out may be stacked onsuitable arbors and se arated by thinsheet metal disks or riggs w 'Iethe baking operation is being pe ormw. lln

facing has been formed may vary with the requirements and. practices ofdifierent manufacturers and may follow that usually employed at thepresent time subsequent to the nnpregnation step. Butthe presentinvention is advantageous in any of these cases in effecting a uniformimpre ation of the product, avoiding the necessity for a separate dopingor impregnating operation and ensuring an absolutely homo neous facing.

It will be understood that t 0 process herein described is by no meanslimited to use with the specific formula above suggested, that formulabeing proposed merely b way of illustration, and that the distinguishingfeature of this process is that the impre nating process is united withthe paper mafiing or sheet forming process by using, for the is made{entirely of asbestos fibre wi 11 a binder, while in other cases asubstantial percentage of Portland cement or of some inert filler, suchas clay, kaolin, or the like, is employed. Various materials are employed as binders besides the crude asphaltum above mentioned, forinstance, bakelite, mineral waxes, and in some cases, a vegetablebinder. The nature of the solvent employed obviously depends upon thenature of the binder used, and the quantity of solvent will depend moreupon mechanical than chemical conditions. That is, the percentage ofsolid matter carried by the iquid as it goes through the paper makingmachine is very small, and the uantity of liquid employed will be controed by the requirements of the paper mahng or sheet forming rocess ratherthan by the necessity for disso ving the binder.

This process completely obviates the very embarrassin dificulty ofproperly impregnating the arcing materia or stock which has beenexperienced heretofore, and facings made according to this process areeven superior in wearing properties than the fabric acings heretoforemore commonly used, When solvents of ave volatile nature are used, suchas gasoline, enzol, and the like, the solvent vapors that escape duringthe process of manufacture may be recovered y processes similar to thoseused for this purppse in other arts, as, for instance, in the rub rcoating industries.

assesses What is claimed as new, is:

l. The process of making blank stock for friction tacings which consistsin mixing the facing materials, including asbestos fibre and a binder,substantially insoluble in water, with a relatively large quantity ofliquid'solvent tor the binder to enable said liquid to hold thematerials in suspension, and then straining out a suficient quantity ofthe solid matter from the mixture to form a blank of suitable term andthickness, whereby said blank will be uniformly impregnated with thebinder.

2. The recess of making blank stock for friction acings which consistsin mining the facing materials, including asbestos fibre and a binder,with a relatively large quantity of liquid hydrocarbon in which thebinder is soluble to enable said liquid to hold the materials insuspension, then running the mixture through a paper making machine andforming therein a sheet of the required thickness, whereby said sheetwill be uniformly impregnated with the binder.

3. The process of forming friction facing stock from finely dividedmaterials includ; ing asbestos fibre and a binder substantiallyinsoluble in water, which consists in utilizing the paper making processto bring said materials into a sheet storm, and using a liquid solventtor-said binder to hold materials in suspension while the sheet is beingformed, whereby said sheet will be uniformly impregnated with thebinder.

4-. The process of forming friction facings from finely dividedmaterials including asbestos and a binder, which consists inutilizharden the facing,

5., its process of forming friction lacing i, a a 1 stock from finelydivided materials including a binder substantially insoluble in wamr,which consists in utilizing the paper making process to bring saidmaterials into a sheet form, and using a liquid solvent for said binderto hold said materials in suspension while the sheet is being termed,cutting facings of the desired term from said sheet,

and then bakinthe lac-in s to cure the binder and hardenthe facing,

In testimony wherein l have signed name to this specification.

WlLLlAl/l G lTLFT.

